1. Field of Invention
The present invention relates in general to the field of contaminant removal. More particularly, the present invention relates to removing sulfur contaminants, especially elemental sulfur (S8), hydrogen sulfide, and other sulfur components, in water using a silicone-based chemical filter.
2. Background Art
Acid-bearing gases in air (e.g., the air within a data center) can lead to a greater incidence of corrosion-induced hardware failures in computer systems and other electronic devices. This problem is especially prone to occur in industrialized countries. Sulfur components (e.g., elemental sulfur, hydrogen sulfide, and/or sulfur oxides) in the air are particularly troublesome gases. It has been demonstrated that the most aggressive of these sulfur-bearing gases is elemental sulfur (S8).
Corrosion of metal conductors caused by sulfur components in the air is especially severe when one or more of the metal conductors is/are a silver-containing metal. Such silver-containing metal conductors are frequently used in electronic devices to electrically connect electronic components. Examples include the silver layer of gate resistors, described below, and many lead-free solders (e.g., Sn—Ag—Cu solder).
A data center is a facility used to house numerous computer systems and various associated systems, such as data storage systems and telecommunications systems. Data centers typically include redundant/backup power supplies, redundant data communications connections, environmental controls (e.g., HVAC, fire suppression, and the like) and security systems. Data centers are also known as “server farms” due to the large number of computer systems (e.g., servers) typically housed within these facilities.
Typically, the environment of a data center is not monitored for the specific nature of gaseous components. This leaves three options: 1) assume that the data center is relatively clean (i.e., the data center environment is MFG Class I or MFG Class II); 2) harden the electronic components of the computer systems and the various associated systems housed in the data center; or 3) filter or scrub the incoming air to the data center. The first option (option 1) leaves at risk the computer systems and the various associated systems housed within the data center. The second option (option 2) drives additional cost (via the purchase of hardened components or use of conformal coatings which provide some level of protection). The third option (option 3) is problematic using current filtering and scrubbing techniques because removing sulfur-bearing gasses in air while letting the remaining gasses pass is very difficult.
With regard to hardening solutions, it is known to cover metal conductors with a conformal coating to protect the metal conductors from corrosion. For example, U.S. Pat. No. 6,972,249 B2, entitled “Use of Nitrides for Flip-Chip Encapsulation”, issued Dec. 6, 2005 to Akram et al., discloses a semiconductor flip-chip that is sealed with a silicon nitride layer on an active surface of the flip-chip. U.S. patent application Ser. No. 12/696,328, entitled “Anti-Corrosion Conformal Coating for Metal Conductors Electrically Connecting an Electronic Component”, filed Jan. 29, 2010 by Boday et al., discloses a conformal coating that comprises a polymer into which a phosphine compound is impregnated and/or covalently bonded. The phosphine compound in the polymer reacts with any corrosion inducing sulfur component in the air and prevents the sulfur component from reacting with the underlying metal conductors. However, as mentioned above, a key disadvantage with such hardening solutions is cost.
With regard to filtering and scrubbing solutions, it is known to remove sulfur-bearing gasses in air using polymer membranes that incorporate functional groups such as amines or phosphines. However, the concentration of the functional group in the polymer membrane is commonly very low (typically, less than 0.1 mole percent) and the functional group will quickly saturate, thus limiting the amount of unwanted gas that can be removed. As the concentration of the functional group in the polymer membrane is increased, the integrity of the membrane suffers greatly. Similarly, polymers that contain a sulfur chelating molecule can no longer absorb sulfur-bearing gases once the sulfur chelating molecule chelates.
As mentioned above, the problem of corrosion caused by sulfur components (e.g., elemental sulfur, hydrogen sulfide, and/or sulfur oxides) in the air is especially severe when one or more of the metal conductors that electrically connect an electronic component is/are a silver-containing metal. For example, each of the gate resistors of a resistor network array typically utilizes a silver layer at each of the gate resistor's terminations. Gate resistors are also referred to as “chip resistors” or “silver chip resistors”. Typically, gate resistors are coated with a glass overcoat for corrosion protection. Also for corrosion protection, it is known to encapsulate gate resistors in a resistor network array by applying a coating of a conventional room temperature-vulcanizable (RTV) silicone rubber composition over the entire printed circuit board on which the resistor network array is mounted. However, the glass overcoat and conventional RTV silicone rubber compositions fail to prevent or retard sulfur components in the air from reaching the silver layer in gate resistors. Hence, any sulfur components in the air will react with the silver layer in the gate resistor to form silver sulfide. This silver sulfide formation often causes the gate resistor to fail, i.e., the formation of silver sulfide, which is electrically non-conductive, produces an electrical open at one or more of the gate resistor's terminations.
FIG. 1 illustrates, in an exploded view, an example of a conventional gate resistor 100 of a resistor network array. A resistor element 102 is mounted to a substrate 104, such as a ceramic substrate. The gate resistor 100 includes two termination structures 110, each typically comprising an inner Ag (silver) layer 112, a protective Ni (nickel) barrier layer 114, and an outer solder termination layer 116. Typically, for corrosion protection, the gate resistor 100 is coated with a glass overcoat 120. Additionally, for corrosion protection, a coating (not shown) of a conventional RTV silicone rubber composition may encapsulate the gate resistor 100. As noted above, it is known to encapsulate gate resistors in a resistor network array mounted on a printed circuit board by applying a coating of a conventional RTV silicone rubber composition over the entire board. However, as noted above, the glass overcoat 120 and conventional RTV silicone rubber compositions fail to prevent or retard sulfur components in the air from reaching the inner silver layer 112. Hence, any sulfur components in the air will react with the inner silver layer 112 to form silver sulfide 202 (shown in FIG. 2). FIG. 2 illustrates, in a sectional view, the conventional gate resistor 100 shown in FIG. 1, but which has failed due to exposure to sulfur-bearing gases. The silver sulfide formation 202 (often referred to as silver sulfide “whiskers”) produces an electrical open at one or more of the gate resistor's terminations 110 because silver sulfide is an electrical non-conductor and, thereby, results in failure of the gate resistor 100.
The use of silver as an electrical conductor for electrically connecting electronic components is increasing because silver has the highest electrical conductivity of all metals, even higher than copper. In addition, the concentration of sulfur components in the air is unfortunately increasing as well. Hence, the problem of corrosion caused by sulfur components in the air is expected to grow with the increased use of silver as an electrical conductor for electrically connecting electronic components and the increased concentration of sulfur components in the air.
The removal of sulfur contaminants in gases and liquids is necessary, or at least desirable, in many industries. For example, acidic sulfur gases must be removed from natural gas in natural gas processing. Refinery gas treatment typically includes sulfur reduction or removal. Sulfur reduction is typically necessary in the production of natural gas liquids (NGLs), diesel fuel and gasoline. Likewise, it is desirable to remove sulfur from well water. Current techniques used in these industries for the removal of sulfur contaminants are costly and inefficient.
Therefore, a need exists for an enhanced mechanism for removing sulfur contaminants, especially sulfur-bearing gases such as elemental sulfur (S8), hydrogen sulfide, and other sulfur components, in fluids (e.g., air, natural gas, refinery gas, and other gases; as well as water, natural gas liquids (NGLs), diesel fuel, gasoline, and other liquids).